Petrenko V. The heat-hydrodynamic processes in the down flowing annular two-phase streams-liquid flow of solutions with the developed wave structure during vaporization

In the dissertation work the results of the complex study of the heat-hydrodynamic processes occurring in the down flowing annular streams of solutions films during evaporation are presented. The results of mathematical modeling of heat transfer processes in laminar and turbulent films of solutions with developed wave structure are presented on the basis of the proposed model of cyclic perturbation of temperature and hydrodynamic fields by large waves during their movement and restoration in the period between passage of large waves. The temperature fields in a film with a developed wave structure in free falling and сo-current vapor flows for viscous laminar and turbulent films are presented as a result of the solution of energy conservation equations; on the basis of which integral characteristics of the heat transfer processes are obtained. Appropriate approximations are given for engineering calculations. The processes of heat transfer to descending annular flows of sugar syrups under vacuum during steam formation were investigated. The processes of heat exchange in films during boiling under the conditions of downward convection are investigated, and the parameters of the delimitation of modes of heat exchange are determined. The results of studies of the processes of heat transfer to annular downward vapor-liquid flows are summarized in a single universal ratio for the calculation of the intensity of heat transfer to juices and syrups, which is valid throughout the range of changes in flow and mode parameters characteristic for the operation of film evaporation plants, concentration of fruit juices. The results of generalizations of hydraulic resistance to down flowing annular stream flows of solutions in the modes of weak and strong phase interaction are given. The results of the analysis of the crisis deterioration of the heat transfer to highly concentrated films of solutions are presented. Based on the results of mathematical modeling of the concentration field in thick films during evaporation, the concept of crisis deterioration of the heat transfer to dense films is formulated, taking into account cyclic mixing of the film with large influent waves. The results of complex modeling of the thermodynamic parameters of down flowing annular streams of solutions occurring in long channels of film evaporative devices are presented.